1. Field of the Invention
This invention relates to low-density nonwoven scouring articles and methods of making same. More particularly, this invention relates to scouring articles comprising a plurality of continuous filaments entangled at a multiplicity of points along their length by needlepunching and having a binder resin coated thereon which further strengthens the articles and which may bind abrasive particles thereto.
2. Discussion of Related Art
The use of lofty, fibrous, nonwoven abrasive products for scouring surfaces such as the soiled surfaces of pots and pans is well known. These products are typically lofty, nonwoven, open mats formed of staple fibers which are bonded together at points where they intersect and contact each other. The staple fibers of low-density abrasive products of this type can be, and typically are, bonded together at points of contact with a binder that may or may not contain abrasive particles. The staple fibers are typically crimped, have a length of about 3.8 cm, a diameter ranging from about 25 to about 250 micrometers, and are formed into lofty open webs by equipment such as "Rando-Webber" and "Rando-Feeder" equipment (marketed by the Curlator Corporation, of Rochester, N.Y. and described in U.S. Pat. Nos. 2,451,915; 2,700,188; 2,703,441 and 2,744,294). One very successful commercial embodiment of such an abrasive product is that sold under the trade designation "Scotch-Brite" by Minnesota Mining and Manufacturing Company of St. Paul, Minn. ("3M"). Low-density abrasive products of this type can be prepared by the method disclosed by Hoover et al. in U.S. Pat. No. 2,958,593.
While such abrasive products have had excellent commercial success, their production requires a considerable investment in equipment. A "Rando-Webber" web-forming machine, for example, can cost in the thousands of dollars. Additionally, the fibers used to form the web of such abrasive products typically require chopping to produce staple fibers which is both costly and time consuming.
Low-density, lofty abrasive products may also be formed of webs or mats of continuous filaments. For example, in U.S. Pat. No. 4,227,350, Fitzer discloses a low-density abrasive product comprising a uniform cross-section, generally flat-surfaced, open, porous, lofty web of autogenously bonded, continuous, undulated, interengaged filaments. The web of Fitzer is formed by downwardly extruding a plurality of thermoplastic organic (e.g. polyamide, polyester) filaments from a spinneret into a quench bath. As the filaments enter the quench bath, they begin to coil and undulate, thereby setting up a degree of resistance to the flow of the molten filaments, causing the molten filaments to oscillate just above the bath surface. The spacing of the extrusion openings from which the filaments are formed is such that, as the molten filaments coil and undulate at the bath surface, adjacent filaments touch one another. The coiling and undulating filaments are still sufficiently tacky as this occurs, and, where the filaments touch, most adhere to one another to cause autogenous bonding to produce a lofty, open, porous, handlable filament web. The web, so formed, is then impregnated with a tough binder resin which adherently bonds the filaments of the web together and also bonds a multitude of abrasive granules, uniformly dispersed throughout the web, to the surface of the filaments. While these products have enjoyed success, their production does have disadvantages. As noted in the patent, one does not necessarily obtain a filament in the quenched web which is identical to the diameter of the extrusion orifice from which it was extruded, which may entail close scrutiny and adjustment of the web forming apparatus, which is time consuming. Further, the webs produced, while conformable to surface irregularities, have limited ability to stretch unless heated to a temperature which might melt the bonds. Adjustment of the degree of autogenous bonding of filaments is difficult without changing the spinneret orifice size or extrusion rate.
Additionally, fibrous polishing and/or abrading materials can be prepared from continuous or substantially continuous synthetic filaments by the method disclosed by Zimmer et al., in U.S. Pat. No. 3,260,582. In this method crimped or curled continuous filaments are straightened out under tension into a substantially parallel relationship with one another, uniformly coated while under tension with an adhesive which may or may not contain abrasive particles, interlocked with one another by release of such tension and then set in a permanently interlocked and lofty, open, 3-dimensional state by curing or setting up the adhesive. However, the continuous filaments of the finished web are substantially parallel, as show in FIG. 2 of the patent. Therefore, to afford a multidirectional high strength web, additional webs having filaments at an angle to the filaments of the first web must be layered onto the first web.
Low-density, lofty, open, porous, nonwoven scouring articles have been more easily and economically manufactured from continuous filaments by the method disclosed by Heyer et al., in U.S. Pat. Nos. 4,991,362, and 5,025,596. The scouring pads described in these patents comprise a multiplicity of crimped or undulated, continuous, thermoplastic organic filaments that are bonded together (e.g., by fusion or an adhesive) at opposite ends. The pad is made by arranging a multiplicity of continuous, crimped or undulated, thermoplastic organic filaments in an open lofty array, with one point of each filament in the array corresponding to a first filament bonding site and a second point of each filament, distant from the first point, corresponding to a second filament bonding site. A pad is formed in the filament array by bonding substantially all of the thermoplastic organic filaments together at the first and second bonding sites. When a pad having greater abrasiveness is desired, abrasive particles may be adherently bonded to the filaments of the pad, preferably before the individual pad is cut from the filament array. These pads have also enjoyed commercial success and are economical to make; however, some users prefer not to have the edges sealed, since they may present discomfort to the hand of the user. Thus, it would be advantageous if continuous filament scouring pads could be easily produced, but without the edge seals, while retaining strength after long time periods of scouring.
U.S. Pat. No. 4,190,550 (Campbell) discloses a seamless, fibrous, soap-filled pad which, when used as a bathing aid, imparts a cleansing and mildly stimulating rubbing action to human skin. A seamless envelope of crimped, resilient, stretchy synthetic staple or continuous organic fibers surrounds a core of solid soap or other surfactant material and is held in integral form solely by the interentanglement of the fibers, such as by needling. The particular problem to be solved was to produce a soap-containing, pad-like article suitable for use on human skin, rather than an article intended for scouring pans or other non-human surfaces. Further, the articles of Campbell, even if suitable for use as a scouring article, do not have the degree of openness required to perform as a kitchen scouring article since when compressed under pressure the nonwoven material is pressed against the bar of soap.
Other background references include U.S. Pat. Nos. 3,688,453; 4,622,253; 4,669,163; 4,902,561; 4,927,432; 4,931,358; and 4,935,295; ; World Patent Application No. WO 92/01536, published Feb. 6, 1992; European Patent Application number 0 492 868 A1, published Jul. 1, 1992; and "Guide to Nonwoven Fabrics", published 1978 by INDA, an association of the nonwoven fabrics industry.
Producers of the scouring pads are invariably seeking ways to minimize cost in manufacturing scouring and abrasive pads and/or tailor the pads for specific uses. The invention described herein is drawn to such methods and articles. To the inventor's knowledge there has not been commercialized or otherwise disclosed an entangled nonwoven scouring article made from continuous, crimped or undulated organic thermoplastic filaments having a binder resin which further strengthens the nonwoven entangled web.